The use of cylindrical mirror analyzers to enable detection of charged particles of a specific energy, (i.e. particle-energy), is well known. Generally, cylindrical mirror analyzers allow charged particles with energies within a certain range of energies, (but not charged particles with energies outside said certain range of energies), which enter thereinto at an angle within an acceptance range of angles, to exit therefrom and be directed into a detector. The presence of a charged particle which transverses a cylindrical mirror analyzer at a detector is a "count-like" indication that said charged particle had an energy within a certain range of energies and entered said cylindrical mirror analyzer at an angle thereto within an acceptance range of angles. In use, parameters of operation, (e.g. applied voltage as discussed supra herein), can be user adjusted and thus allow selection of: EQU "energy--charged-particle--angle of entry"
combinations that can pass through a relatively fixed geometry cylindrical mirror analyzer system, and be subsequently detected.
To aide with understanding of the present invention it must be understood that cylindrical mirror analyzers generally comprise two finite length, elongated, concentric essentially tubular shaped elements, (i.e. outer and central-most), which two finite length elongated concentric essentially tubular shaped elements are typically of a functional, essentially equal, length. Each of said two elongated concentric essentially tubular shaped elements is preferably, but not necessarily, essentially circular shaped in cross-section, and the central-most concentric essentially tubular shaped element has holes through the tubular wall thereof near each longitudinally opposed end thereof, such that in use, charged particles can enter and exit the formed annular space between said outer and central-most elongated concentric essentially tubular shaped elements through holes at first and second ends, respectively, of said central-most concentric essentially tubular shaped element.
In use, a voltage is applied between the outer and central-most concentric essentially tubular shaped elements such that an electric field is effected in said formed annular space therebetween, and such that charged particles which enter into said annular space at some energy related velocity and trajectory locus angle, via said a hole through the first end of the tubular wall of said central-most elongated concentric essentially tubular shaped element, are guided in their further trajectory locus through, and out of, said annular space. Entering charged particles with an energy, (i.e. velocity), within a range which is determined by the applied voltage across the two elongated concentric essentially tubular shaped elements, (and the roughly the distance from said first hole, to a second hole through the central-most essentially tubular shaped element wall), will be guided so as to exit said annular space between said outer and central-most essentially tubular shaped elements, through a second hole through the wall of said central-most elongated concentric essentially tubular shaped element, at the opposed longitudinal, (e.g. second), end of the central-most elongated concentric essentially tubular shaped element. A detector for detecting charged particles is typically positioned to intercept said exiting charged particles. Charged particles which do not enter the annular space, or which enter at other than an angle within a range of acceptance angles, or which have an energy outside the "detection" range, (which again is determined by the applied voltage and distance between said first and second holes through the wall of the central-most elongated concentric essentially tubular shaped element), will not be guided in their trajectory locus so as to exit the annular space through said hole through the wall of said at the opposed, second, longitudinal end of the central-most elongated concentric essentially tubular shaped element. Instead such charged particles with energies outside the "detection" range etc. will typically collide with, for instance, the inner surface of the essentially tubular shaped wall of the outer elongated concentric essentially tubular shaped element, or the outer surface of the essentially tubular shaped wall of the central-most elongated concentric essentially tubular shaped element. Assuming a charged particle has an entry trajectory locus angle within a range of acceptance angles, it can then be appreciated that only particles which have an energy, (i.e. mass, charge and velocity), within a "detection" range, and which enter the identified annular space, can be expected to reach the indicated detector through a cylindrical mirror analyzer. It should also be appreciated that the "detection" range of energies of charged particle which are guided into the detector for detecting charged particles of a given charge, is easily user determined by adjustment of the voltage applied between the two, (outer and central-most), concentric essentially tubular shaped elements and the electric field formed in said annular space as a result. Within limits, this is the case regardless of fixed physical distance between the first and second holes in the wall of the central-most elongated concentric essentially tubular shaped element, as voltage applied between the two, (outer and central-most), concentric essentially tubular shaped elements is continuously adjustable over a practical range. It is also noted that charged particles have associated therewith mass, and because the trajectory of a charged particle moving in an electric field is effected by said charged particle mass, cylindrical mirror analyzers can, alternatively, be employed as a mass-spectrometer, similar to a time of flight mass-spectrometer, where the magnitude of the charge present is known.
Representative, non-limiting sources of energetic charged particles which can be analyzed by cylindrical mirror analyzers include Auger, electron photoemission, and low energy positive ion scattering systems. That is, particles with either positive or negative charge can be detected. A particularly relevant source of charged particles is a material sample system which is caused to be bombarded by a source of energetic excitation, such as a beam of electrons, photons or ions. As a result of interaction between said bombarding particles, or photons, and said material sample system, charged particles are emitted from said material sample system.
Until recently, typical known cylindrical mirror analyzers were large and bulky and required fixed placement, or placement on a bulky position manipulator. This was the case as to attain high resolution charged particle-energy detecting, large diameter elongated concentric essentially tubular shaped elements, (i.e. outer and central-most), were thought to be necessary. A 1996 Patent to Dowben et al., U.S. Pat. No. 5,541,410, however, described a single pass cylindrical mirror analyzer of a relatively reduced diameter and size, which reduced size single pass cylindrical mirror analyzer, could be easily mounted on a flange mounted linear motion feedthrough, such that insertion and retraction of said reduced size single pass cylindrical mirror analyzer, to and from a position at which charged particles to be detected were present, the energies of which charged particles are to be investigated, could be easily achieved utilizing, for instance, a bellows-type linear motion feedthrough means. This ease of adjustment, it is noted, provided a major advantage and improvement over then existing cylindrical mirror analyzer systems. Continuing, typical outer and central-most concentric essentially tubular shaped elements in the system described in the 410 Patent are, for the outer concentric essentially tubular shaped element, in the range of thirty (30) to fifty (50) millimeters, and for the central-most concentric essentially tubular shaped element, in the range of fifteen (15) to forty (40) millimeters. The length of the 410 Patent cylindrical mirror analyzer system was disclosed as being approximately forty-five (45) millimeters. It is also noted that the 410 Patent system is dimensioned so as to accept charged particles which enter thereto along a trajectory locus oriented at an optimum acceptance angle of forty-two (42) degrees-eighteen-and-one-half (18.5) minutes with respect to the longitudinal locus of the single pass cylindrical mirror analyzer. It is further noted that said 410 Patent single pass cylindrical mirror analyzer further comprises a cylindrical housing having first and second ends positioned to generally coincide with first and second ends of the outer and central-most finite length elongated concentric essentially tubular shaped elements, said cylindrical housing being concentrically positioned outside and around said outer essentially tubular shaped concentric element. The cylindrical housing further comprises, at the first end thereof, a typically conical cap which presents with an aperture located therein for allowing charged particles to enter. At the second end of said 410 Patent single pass cylindrical mirror analyzer, there is present a manipulator for use in manipulation of the retractable single stage cylindrical mirror analyzer system into a position wherein charged particles can enter thereto. Said manipulator can be affixed to a bellows-type linear motion feedthrough in use, and the entire assembly can be mounted on a vacuum flange having a diameter in the range of seventy (70) to two-hundred (200) millimeters, inclusive, including a conflat type flange.
While the benefits of the 410 Patent reduced size single stage, single pass cylindrical mirror analyzer are significant, (with focus being on the ease of mounting and positioning thereof in a vacuum system), it has been found that greater charged particle-energy detection resolution than can typically be achieved by its use, would be very desirable. The present invention teaches that greater charged particle-energy detection resolution is achieved by a compact, small diameter, high charged particle-energy detection resolution, "multiple sequential stage", retractable cylindrical mirror analyzer system which, in use, enables charged particle-energy detection with an improved resolution over that possible where single stage, compact, small diameter, retractable cylindrical mirror analyzers are utilized.
Additional, less relevant, known Patents which were cited in the 410 Patent are U.S. Pat. Nos. 4,048,498 and 4,205,226 to Gerlach et al. and Gerlach respectively, and U.S. Pat. No. 5,099,117 to Frohn et al.
Another, less relevant, Patent of which the inventor is aware is U.S. Pat. No. 3,783,280 to Watson. In the Watson 280 Patent, FIG. 5 is specifically identified as it shows a typical cylindrical mirror double pass configuration wherein a pair of inner (62) and outer (63) coaxial cylindrical tubular electrodes are present. It is noted that multiple holes (61), (65), (68) and (69) through which charged particles can pass are present in the continuous inner cylindrical tubular electrode. It is further noted that a charged particle passing through the entire FIG. 5 configuration follows a locus which is roughly a full sinusoid-like cycle and that the same electric field is encountered by such a charged particle in the annular space between inner (62) and outer (63) coaxial cylindrical tubular electrodes for said charged particle entering thereinto through hole (61) or hole (68). That is, there is nothing in Watson 280 to indicate that the inner electrode (62) is not electrically continuous over its entire length.
U.S. Pat. Nos. 3,935,453 and 3,949,221 to Liebl describe the presence of multiple electrodes in a cylindrical mirror system, but said multiple electrodes are configured in a single pass arrangement.
Other patents which describe cylindrical mirror systems, of which the Inventor is aware, are:
U.S. Pat. No. 4,769,542 to Rockett; PA1 U.S. Pat. No. 4,218,617 to Cazaux; PA1 U.S. Pat. No. 3,761,707 to Liebl; PA1 U.S. Pat. No. 4,593,196 to Yates; PA1 U.S. Pat. No. 4,860,224 to Cashell et al.; PA1 U.S. Pat. No. 5,032,723 to Kono; and PA1 U.S. Pat. No. 4,849,641 to Berkowitz. PA1 a. a concentric outer essentially tubular shaped element having a tubular wall with an inner surface, and first and second ends; PA1 b. a concentric central-most essentially tubular shaped element having a tubular wall with an outer surface and first and second ends, with holes through said tubular wall being present near both said first and second ends thereof, said central-most essentially tubular shaped element being present within said concentric outer essentially tubular shaped element such that an annular space is formed between the inner surface of the tubular wall of said outer essentially tubular shaped element and the outer surface of said tubular wall of said central most essentially tubular shaped element; PA1 c. means for applying electrical potential to each of said concentric outer and central-most essentially tubular shaped elements to the end that an electric field is formed in said annular space between said concentric outer and central-most essentially tubular shaped elements. PA1 a. a concentric outer essentially tubular shaped element having a tubular wall with an inner surface, and first and second ends; PA1 b. a concentric central-most essentially tubular shaped element having a tubular wall with an outer surface and first and second ends, with holes through said tubular wall being present near both said first and second ends thereof, said central-most essentially tubular shaped element being present within said concentric outer essentially tubular shaped element such that an annular space is formed between the inner surface of the tubular wall of said outer essentially tubular shaped element and the outer surface of the tubular wall of said central most essentially tubular shaped element; PA1 c. means for applying electrical potential to each of said concentric outer and central-most essentially tubular shaped elements to the end that an electric field is formed in said annular space between said concentric outer and central-most essentially tubular shaped elements. It is specifically pointed-out that said means for applying electrical potential to each of said concentric outer and central-most essentially tubular shaped element is not limited to effecting a ground potential at the central-most essentially tubular shaped element, as was the case in the Dowben 410 Patent System and as was described in the article titled "A Novel Design For A Small Retractable Cylindrical Mirror Analyzer" by Mcllroy, Dowben & Ruhl, which appeared in the J. Vac.Sci. Technol. B, 13(5) Sep/Oct 1995, as cited in the Background Section of this Disclosure. PA1 a. providing a single stage retractable cylindrical mirror analyzer as described infra herein: PA1 b. by manipulation of said manipulator causing said first end of said retractable cylindrical mirror analyzer to be positioned near charged particles, the energy of which is to be detected; PA1 c. causing electric fields to exist in the annular space of each present cylindrical mirror analyzer stage; PA1 a. providing a compact, small diameter, high charged particle energy detection resolution, multiple sequential stage, retractable cylindrical mirror analyzer system as described infra herein; PA1 b. by manipulation of said manipulator, causing said first end of said first sequential stage cylindrical mirror analyzer to be positioned near charged particles, the energy of which is to be detected; PA1 c. causing electric fields to exist in the annular space of each present cylindrical mirror analyzer stage;
Scientific articles of which the inventor is aware which describe particle energy analyzing cylindrical mirrors and/or analysis or use thereof are:
1. "A Novel Design For A Small Retractable Cylindrical Mirror Analyzer", Mcllroy, Dowben & Ruhl, J. Vac. Sci. Technol. B, 13(5) Sep/Oct 1995. This reference describes a single pass system, in which the inner cylinder electrode is held at ground potential. PA0 2. "Angle-Resolving Photoelectron Energy Analyzer: Mode Calculations, Ray-Tracing, Analysis and Performance Evaluation", Stevens et al., J. of Electron Spectroscopy and Related Phenomena 32 (1983). PA0 3. "Analysis Of The Energy Distribution In Cylindrical Electron Spectrometers", Aksela, The Review of Scientific Instruments, Vol. 42, No. 6, (1971). PA0 4. "An Electrostatic Mirror Spectrometer With Coaxial Electrodes For Multi-Detector Operation", Wannberg, Nuclear Instruments and Methods, 107 (1973). PA0 5. "Cylindrical Capacitor As An Analyzer* I. Nonrelativistic Part", Sar-El, The Review of Scientific Instruments, Vol. 38, No. 9, (1967). PA0 6. "Internal Scattering In A Single Pass Cylindrical Mirror Analysis", Bakush et al., J. of Electron Spectroscopy and Related Phenomena 74, (1995). PA0 7. "On The Image Properties Of An Electro-Static Cylindrical Electron Spectrometer", Karras et al., Annals Academiae Scientiarum Fennicae, (1968). PA0 8. Criterion For Comparing Analyzers", Sar-El, The Review of Scientific Instruments, Vol. 41, No. 4, (1969). PA0 9. "Adsorbtion And Bonding Of Molecular Icosahedra On Cu(100)", Zeng et al., Surface Science, 313 (1994).
It is also noted that the present Application is commonly owned with the 410 Patent, (which is incorporated herein by reference). It is in that light that some claims in the present Disclosure are focused on single stage, (i.e. single-pass), compact, small diameter, retractable cylindrical mirror analyzers without the limitation of a grounded inner cylindrical electrode.